Ok, we just had our 08 MCS engine rebuilt, we had a cracked #3 piston, so they replaced all 4 and did new bearings and everything else.

Mods are full Alta intake and piping, Alta IC, Alta Turbo back exhaust and Evolve Tune. Car has 96kmi on it, engine has less then 1000mi on the rebuild.

The other day there was a dramatic loss of power and a very weird turbo noise. It is a more of a hissing with a gurgling type of sound. Under light throttle the car feels drives fine, but it's very low of power.

I looked around and don't see any hoses off or loose, but have not been under the car. I also pulled off the cold side and felt the turn shaft it's tight and spins.

My thought is the DV is leaking or I have a slight boost leak.? But there are no CEL's either active or stored.

 

check your boost tubes, your turbo pipes leading to front mount all the way back to the throttle body.

 

Went over the entire intake path found the hose clamp on the throttle body to be on at a angle. In normal simple driving it was good, when you got any kind of boost it would leak.

Funny that the car ran like crap with no power, but there was no CEL, either the engine light, or stored codes.

 

Your ecu was compensating for the air leak. So it would run safely but choppy and unsmooth. Not ideal operating condition but not overly alarming to the ecu either.

 

Should be A-ok now. What was the reason for cracking piston 3?

 

Yea, I understand the ECU will compensate, but a boost leak should trigger a CEL.

Hoping everything is ok now. Not sure what cracked the piston, one thought is things got a bit hot when the HPFP was going out. The car is a daily driver and not driven hard, and very rarely goes to redline.

 

a boost leak that only presents itself under positive pressure won't always throw a cel, the ECU will see it as under boosting and will adjust wastegate duty up to compensate in order to hit target loads. once the wastegate duty has hit the limit of compensatory range, it will throw a code.

 

I had to floor it to go up a hill I usually use about 1/4th throttle for. It sounded horrible, like the turbo was over spooling.

Maybe I didn't drive it like that enough, but my thought was a CEL should have been triggered.